Agricultural Experiment Stations rated bird 

 depredations as their second most urgent 

 problem. One of the first steps Branch 

 personnel have taken in their efforts to find 

 a solution to the problem has been to learn 

 where the depredating birds breed and 

 where they winter. For this reason, trapping 

 and banding operations were accelerated in 

 the Atlantic and Mississippi Flyways in 

 1961. Patuxent Wildlife Research Center 

 biologists banded 22,000 starlings and black- 

 birds, including 5,500 redwinged blackbirds. 

 Volunteer cooperators banded 3,200 nestling 

 redwings. An immediate result was learning 

 that birds damaging the Arkansas rice crop 

 were locally bred birds--birds coming into 

 Arkansas from the north in fall and early 

 winter get there after the rice has been 

 harvested and therefore are not part of the 

 local problem. 



tLuxtiis wem 



.1 HAjn 

 tfDTTa tuuzjtm loosn 

 Lac«tad «• ol Much 1961 



Locations of 41 major blackbird roosts In southeastern 

 United States. Each of these roosts contained a million 

 birds or more. Three contained 10 to 20 million birds 

 each. 



In the vicinity of the Sand Lake National 

 Wildlife Refuge, South Dakota, however, 

 Bureau personnel and cooperators who 

 banded 2,500 blackbirds learned that only a 

 small fraction of the birds causing serious 

 damage to corn were locally produced. 



Focal points of blackbird populations were 

 located through a cooperative search for 

 fall and- winter roosts in eastern States. 

 Fifty major roosts, each containing a million 

 or more birds, were located. Three of these 

 roosts contained from 10 to 20 million birds 

 each. 



To discover the weak link in the makeup 

 of birds, basic avian physiological studies 

 are being conducted at the Massachusetts 

 Cooperative Wildlife Research Unit. This 

 work may provide guidelines as to whether 

 the sight, taste, hearing, or other sensory 

 systems are most vulnerable. 



Reproductive inhibitors . --The Massachu- 

 setts Cooperative Wildlife Research Unit is 

 investigating the possibility of controlling 

 depredating bird populations by steriliza- 

 tion, a technique used effectively against 

 the screwworm fly in the Southeast. Ex- 

 perimentation with three oral progestin hor- 

 mones indicated excellent potential for in- 

 hibiting bird reproduction. Lipamone, a 

 female sex hormone, failed to block egg 

 production. High-energy microwave ex- 

 posure had no observed effects on fertility 

 of chickens, quail, and exposed eggs. Enhep- 

 tin fed to nesting gulls proved to be inef- 

 fective in inhibiting reproduction, although 

 this chemical has high potency in this ob- 

 jective with other species. Investigations 

 are underway, also, to determine whether 

 radioactive perches might cause avian 

 sterility. 



At the Denver Center experiments have 

 been initiated to develop reproductive in- 

 hibitors as a means of regulating coyote 

 numbers. Later the studies will be ex- 

 tended to include other control chemicals 

 such as antimetabolite and antifolic agents. 



28 



